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Red Crab Invasion At San Diego Beaches May Signal Coming El Niño

Photo by Susan Murphy

Tuna crabs blanket the shoreline at Ocean Beach in San Diego, June 12, 2015.

Massive numbers of small red crabs that normally inhabit the warm waters off of Baja California have invaded San Diego’s beaches — from Ocean Beach to La Jolla.

Massive numbers of small red crabs that normally inhabit the warm waters off of Baja California have invaded San Diego’s beaches — from Ocean Beach to La Jolla. The likely reason: the region's above-average ocean temperatures.

The 4-inch-long crustaceans, commonly called tuna crabs, have washed ashore with the tides during the past two weeks.

Photo by Susan Murphy

Beachgoers look at Tuna crabs on Mission Beach, June 12, 2015.

The miniature, lobster-looking creature spends most of its life-cycle floating freely between the ocean bottom and the surface, in warm tropical waters.

The rare crab strandings that San Diego is experiencing could be an indicator of a building El Niño, said Linsey Sala, a museum scientist and collection manager of the pelagic invertebrates collection at Scripps Institution of Oceanography in La Jolla.

"We typically see them en masse in warm water intrusion events," Sala said.

"They’re subject to changing winds, tides, currents and sort of being pushed in different directions and subject to those different oceanographic conditions," she said.

Sala said the last time the crabs appeared in droves on San Diego’s beaches was during the El Niños of 1998 and 2002.

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